Expansion bolt



Jan. 13, 1953 w. J. LEWIS 2,625,071

EXPANSION BOLT Filed Oct. 51, 1950 2 SHEETS SHEET 1 I: ggxwgsa up I IN V EN TOR.

WARREN J. LEWIS ATTORNEY Jan. 13, 1953 W. J. LEWIS EXPANSION BOLT Filed Oct. 51, 1950 HH I [ll 2 SHEETS-SHEET 2 IINVENTOR.

WARREN J. LEWIS i9? Z/hd' ATTORNEY Patented Jan. 13, 1953 EXPANSION BOLT Warren J. Lewis, Mansfield, Ohio, assignor to The Ohio Brass Company, Mansfield, Ohio, a corporation of New Jersey Application October 31, 1950, Serial No. 193,170

1 Claim.

' This invention relates to expansion bolts. More particularly, it relates to the type of expansion bolts used for supporting the roof of a mine tunnel or the like. The bolts are installed in holes drilled into the roof of the mine and with the efficient drilling apparatus now available the installation of these bolts is a very simple and inexpensive matter as compared with the former practice of shoring the roof and sides of a mine tunnel with large timbers.

,The improved expansion bolt of this invention includes a relatively long rod or stud on which the expansible portion of the bolt is assembled. The bolt is inserted into a hole drilled into the mine roof, with the expansible portion deep in the hole. The lower end of the stud which is at the mouth of the hole supports means such as a plate or the like which covers the mouth of the hole and holds in place a relatively large area of the surface of the mine surroundin the hole. The expansible portion of the bolt is composed essentially of a multi-section shell, the several sections of which are positioned axially around the stud and held in place by an expansible ring or the like. After the expansion bolt has been properly located in a hole the stud is rotated and these shell sections are forced apart and pressed tightly against the sides of the hole by an expander which is threaded onto the stud. The inner ends of the sections are engaged with a portion of the stud which is threaded reversely to the portion onto which the expander is screwed so that the shell and the expander are moved relatively toward one another when the stud is rotated. Consequently, the expansion action is very rapid. When resistance occurs to the movement of the shell and stud toward one another, continued rotation of the stud forces the parts of the shell laterally as the thread on the shell rides up on the thread on the stud.

As the stud is rotated to press the shell sections against the wall of the hole, the retaining means which holds the sections in assembled relation yields to the pressure exerted by the expander. The sections may be moved outwardly away from the studsufficiently to separate them from their threaded engagement with the stud.

Further rotation of the stud causes the expander to advance along its thread to press the shell sections tightly against the sides of the hole without any further movement of the sections into the hole, and at the same time the stud is drawn upwardly into the hole so that the plate is pressed tightly against the surface of the mine roof.

A preferred form of the invention is illustrated in the drawing. In the drawing-- Fig. 1 is a view showing the expansion bolt when it is initially positioned in a hole drilled into a mine roof;

Fig. 2 is a view similar to Fig. 1 but showing the bolt after it has been partially expanded;

Fig. 3 is a view similar to Fig. 1 but showing the bolt further expanded and in tight engagement with the sides of the hole;

Figs, 4 and 5 are cross sectional views taken on the lines l4 and 5-5, respectively, of Fig. 1; and

Fig. 6 is a cross-sectional view taken on the line 66 of Fig. 2.

The preferred form of the expansion bolt includes a stud l which is relatively long; usually the stud will be from two to six or seven feet long. A substantially flat plate 2 encircles the lower end of the stud and is supported by the head 3 of the stud. When the bolt is put in the drilled hole 4, as shown in Fig. 1, the plate 2 covers the mouth of the hole. Ihe plate 2 will be tightened against the roof 5 of the mine as the bolt is expanded.

The opposite end of the stud is provided with a right-hand thread 6 onto which the threaded central opening 1 of the expander 8 is threaded. The expander is of the conventional type. It is shaped like a cone frustrum except for the ribs 9 which prevent rotation between the expander and the expansible sections of the bolt, as described below. The outer, smooth surface N3 of the expander tapers from a smaller diameter at end I l to a larger diameter at end l2. The smaller end ll of the expander points towards the head or lower end of the stud.

The expansible portion of the bolt is formed in two sections [3 and M which are assembled around the stud to form a shell below the expander. Each of the shell sections l3 and M has two tongues l5 and I5, respectively (see Fig. 4), which are spaced by longitudinal slots [6 and l 6', respectively. When the sections are assembled, the adjacent tongues I5 and I5 on the two sections are separated by the slots ll which are the same size as the slots l6 and [6. Half of each slot H is formed on each section of the shell so that when the sections are assembled these halves mate to form the slots I 1 on opposite sides of the shell. Two or more sections may be used, but no one section will extend more than 180 around the stud since the sections are adapted to be moved radially away from the stud.

The tongues I5, [5 of the shell sections each cover no more than of the surface of the stud. They are relatively thin at their tips and gradu- 4 3 ally become thicker towards the bottom of the slots I8 ,I 6' and I1. At the start of any operation .(Fig. 1) the outer surfaces of the shell sections are substantially cylindrical. The inner surfaces 2| then taper gradually inward to the location being spaced farthest from the stud at their tips. The angle of this taper is less than the angle atwhich the outer surface of the expander tapers. For instance, the wall [0 of the expander may slope outwardly at an angle of eight degrees, and the inner wall of the tongues may slope at an angle of four degrees. Then as the expander is drawn down into the multi-section shell, the sections of the shell are pressed outwardly and embedded in the wall of the hole 4 in the roof of the mine. The outer surface is advantageously provided with fiutes 22 to get a better grip on the material in which the hole 4 is located.

The end 23 of each shell section below the slots is provided with a segment of a left-hand thread. When the sections are assembled on the stud the threaded portions of the several sections cooperate to form a complete left-hand, internal thread which is engaged with the lefthand thread 25 on the stud, below the righthand thread 5. When the bolt is inserted in a hole, sections are heldin engagement with this thread 25 by the ring (it in the groove 3! in the outside of the lower end of the sections.

This ring Sil may be of a pliable wire or rubber,

or may be of any expansible construction. The ring shown is not continuous. The ends abut each other as indicated at numeral 33. The ring is sufficiently elastic to be snapped into place in the groove 31 after the sections are properly positioned.

The sections are assembled so that the lower end it of the expander fits against the inner surface 2i 'of the tongues, near their tips, as shown in Fig. 1. Ribs 9 fit into the slots 11 between the shell sections in the manner shown in Fig. l. The sections may equally well be assembled with the ribs 9 in the slots l6 and IS. The ribs 9 prevent any relative rotation between the shell sections and the expander when the stud l is rotated.

, To tighten the expansion bolt in the hole 4 the stud is rotated in a clockwise direction. As the stud is rotated the expander and shell sections move relatively toward each other along their respective threads. The expander simultaneously presses the shell sections outwardly, starting at their tips. This flares the tips outwardly as shown in Fig. 1. As the expander enters further and further into the shell, the ring 3-8 yields and the sections are moved further from the stud (Fig. 2) until eventually the internal threads on the shell become completely disengaged from the threads 25 on the stud (-Fig. 3). Thereafter there is no further longitudinal movement of the shell with respect to the stud. Upon rotation of the stud, after the threads have become disengaged, the expander continues to move along the thread 6 and, as it is drawn further and further into the shell it presses the shell sections farther and farther from the stud and embeds them more tightly in the sides of 4 the hole. The expander is capable of exerting extremely high pressure on the tongues and the ultimate position to which the expander will be moved will depend on the hardness of the stratum into which the hole is drilled.

As the expander is drawn into the shell, the plate -2 is drawn up tightly against the surface of the mine roof, covering the hole. The plate may become embedded in the surface somewhat as shown in Fig. 3.

After the plate is in pressure contact with the roof of the mine the thread 6 may bind against thethread through the opening I of the expanderfso that the expander will have a tendency to rotate with the stud as the stud is turned. If this occurs the ribs 9 will press against the edges of their respective slots and tend to rotate the shell sections also. This does no harm.

The deeper the expander is drawn into the shell, the greater the outside diameter of the shell becomes, and the tighter the bolt is held in the hole. The expander can produce an enormous outward pressure on the shell sections. The sections are preferably made of malleable iron so that the tongues will bend under the pressure of the expander.

This expansion bolt is particularly eificient and is easily manufactured and installed. The threads on the stud. may be rolled or cut in any suitable manner.

The invention is in the appended claim.

What I claim'is:

In an expansion bolt composed of a plurality of independent shell sections, a stud threaded at its outer end, yieldable retaining means around the inner end of the shell sections and holding them to the stud, and an expander threaded on the outer end of the stud with at least a part thereof within the outer end of the shell sections and adapted to spread the shell sections as the expander is turned further on to the stud, the improvement which consists 'in the provision of 'a thread on the stud located inwardly from the -aforementioned thread and threaded in the reverse direction from the aforementioned thread, and threads on the inner surface of the shell sections near their inner end which cooperate with said reverse threads 'on the stud whereby when the stud is turned and the expander enters sr'uliciently far into the shell sections the reverse threads spread the inner ends of the shell sections laterally against the yieldable retaining means.

WARREN J. LEWIS.

REFERENCES CITED The following references are of record in the file of this patent:

uNf'rED STATES PATENTS Number Name Date 13,177 London 'et al. July 3, 1855 691,921 Wheeler Jan. 28, 1902 927,064 Mower July 6, 1909 1,372,291 Jacobs Mar. 22, 1921 1,434,394.- 'Matthes Nov. 7, 1922 2,521,065 Kempton Sept. 5, 1950 

